1. Field of the Invention
This invention relates to a method of producing a sintered ceramic body with excellent degreasing efficiency and sintering properties, and to a method of producing a sintered ceramic body with stable and high quality. More particularly, the invention relates to a method of producing a ceramic wiring board.
This invention is applicable to a wide range of industrial fields where there is need for a dense sintered ceramic body, such as IC packages, thick- or thin-film substrates and glazed substrates.
2. Description of the Prior Art
Heretofore, ceramic base particles for use in the production of, for instance, a multilayer ceramic wiring board have been used with control of only the average particle diameter thereof.
Also, a sintering assistant powder added in the production of sintered ceramic body has hitherto been used with control of only the average particle diameter thereof. A method of improving sintering properties by reducing the average particle diameter of the assistant powder has also been known.
In the conventional method of producing a sintered ceramic body as mentioned above, the powder to be sintered is usually fired at a temperature of 1400.degree. to 1600.degree. C. in a non-oxidizing atmosphere. When ceramic base particles having a large average particle diameter are used, in general, a considerable number of ceramic base particles of large size are present in the powder to be sintered. The large particles causes nonuniform sintering, leading to higher possibility of void formation, so that a sufficient increase in sintered density is not achieved. Use of ceramic base particles with a small average particle diameter, on the other hand, generally fails to increase the sintered density where firing is conducted in a non-oxidizing atmosphere, though the sintering property of the ceramic base particles is enhanced. Thus, the use of the ceramic base particles with a small average particle diameter does not always yields a sintered body of enhanced quality.
Even when only the average particle diameter of the sintering assitant powder is specified as mentioned above, the assistant powder generally shows wide dispersion of particle size and, therefore, a considerable number of coarse particles are present in the powder. Accordingly, large voids exceeding about 15 to 20 .mu.m in diameter may be formed in the inside or the surface of the sintered body. The presence of such large voids impairs the stability of electrical and mechanical properties and the like which the sintered body would intrinsically have. Especially in the case of a wiring board, the presence of the large voids would cause breakage of a thin film formed on the board or dispersion of resistance values, leading to deterioration of thermal shock properties or to nonuniformity of strength.